Sanitary filtration plants of the above type are known which comprise joined helical filter elements connected in series and mounted inside a pressure pipe, and where the product in question passes through the filter member while subjected to a suitable pressure difference. From the filter member, the permeate flows into the connected central tubes and leaves said tubes while separated from the concentrate. The concentrate passes through the filter member and leaves the pressure pipe while separated from the permeate. The helical filter elements can be of a length of approximately 0.5 to 1.0 m and have a tendency to be subjected to an axial displacement of the filter member relative to the central tube, viz. a so-called telescoping. Therefore, supporting means are arranged between the helical filter elements in order to counteract said displacement, said supporting means being so-called anti-telescoping devices, viz. ATD's. These supporting means also serve to ensure that the product to be filtered does not pass the filter elements freely between the external periphery thereof and the inner side of the tubular pressure vessel as a slit is provided at this location. This slit originates from an overdimensioning of the pressure vessel and allows an easy mounting and replacement of the filter elements. The latter prevention of the free flow through this slit is enhanced by the supporting means comprising a sealing means along the external periphery.
A filtration device with supporting means of a similar type is known from U.S. Pat. No. 4,517,085. However, this helical filtration device is not suited for use as a sanitary filtration plant.
A sanitary filtration plant used inter alia within the dairy, the medicine and the food-stuff industry presents very high requirements to the hygiene. A continuous use of a sanitary filtration plant often necessitates a cleaning, such as once or twice a day, whereby a cleaning fluid passes through the plant. It is important in connection with such a cleaning process that residues of the product in question are removed.